NAME

SYNOPSIS

DESCRIPTION

mknod creates a FIFO (named pipe), character special file,
or block special file with the specified name.
A special file is a triple (boolean, integer, integer)
stored in the filesystem. The boolean chooses between char-
acter special file and block special file. The two integers
are the major and minor device number.
Thus, a special file takes almost no place on disk, and is
used only for communication with the operating system, not
for data storage. Often special files refer to hardware dev-
ices (disk, tape, tty, printer) or to operating system ser-
vices (/dev/null, /dev/random).
Block special files usually are disk-like devices (where
data can be accessed given a block number, and e.g. it is
meaningful to have a block cache). All other devices are
character special devices. (Long ago the distinction was a
different one: I/O to a character special file would be
unbuffered, to a block special file buffered.)
The mknod command is what creates files of this type.
The argument following name specifies the type of file to
make:
p for a FIFO
b for a block (buffered) special file
c for a character (unbuffered) special file
The GNU version of mknod allows u (`unbuffered') as a
synonym for c.
When making a block or character special file, the major and
minor device numbers must be given after the file type (in
decimal, or in octal with leading 0; the GNU version also
allows hexadecimal with leading 0x). By default, the mode
of created files is 0666 (`a+rw') minus the bits set in the
umask.

OPTIONS

-mmode, --mode=mode
Set the mode of created directories to mode, which can
be symbolic as in chmod(1) and then uses the default
mode as the point of departure.

GNU STANDARD OPTIONS

CONFORMING TO

POSIX does not describe this command as it is nonportable,
and recommends using mkfifo(1) to make FIFOs. SVID has a
command /etc/mknod with the above syntax, but without the
mode option.

NOTES

On a Linux system (version 1.3.22 or newer) the file
/usr/src/linux/Documentation/devices.tex contains a list of
devices with device name, type, major and minor number.
The present page describes mknod as found in the fileutils-
3.16 package; other versions may differ slightly. Mail
corrections and additions to aeb@cwi.nl and
aw@mail1.bet1.puv.fi and ragnar@lightside.ddns.org . Report
bugs in the program to fileutils-bugs@gnu.ai.mit.edu.